Physiological characteristics of gastric contractions and circadian gastric motility in the free-moving conscious house musk shrew (Suncus murinus)

Abstract

Physiological characteristics of gastric contractions and circadian gastric motility in the free-moving conscious house musk shrew (Suncus murinus). Am J Physiol Regul Integr Comp Physiol 299: R1106 -R1113, 2010. First published August 4, 2010 doi:10.1152/ajpregu.00278.2010.-Although many studies have demonstrated the physiological action of motilin on the migrating motor complex, the precise mechanisms remain obscure. To obtain new insights into the mechanisms, we focused on the house musk shrew (Suncus murinus, suncus used as a laboratory name) as a small model animal for in vivo motilin study, and we studied the physiological characteristics of suncus gastrointestinal motility. Strain gauge transducers were implanted on the serosa of the gastric body and duodenum, and we recorded gastrointestinal contractions in the free-moving conscious suncus and also examined the effects of intravenous infusion of various agents on gastrointestinal motility. During the fasted state, the suncus stomach and duodenum showed clear migrating phase III contractions (intervals of 80 -150 min) as found in humans and dogs. Motilin (bolus injection, 100-300 ng/kg; continuous infusion, 10-100 ng · kg Ϫ1 · min Ϫ1 ) and erythromycin (80 g·kg Ϫ1 · min Ϫ1 ) induced gastric phase III contractions, and motilin injection also increased the gastric motility index in a dose-dependent manner (P Ͻ 0.05, vs. saline). Pretreatment with atropine completely abolished the motilin-induced gastric phase III contractions. On the other hand, in the free-feeding condition, the suncus showed a relatively long fasting period in the light phase followed by spontaneous gastric phase III contractions. The results suggest that the suncus has almost the same gastrointestinal motility and motilin response as those found in humans and dogs, and we propose the suncus as a new small model animal for studying gastrointestinal motility and motilin in vivo.suncus; migrating motor complex; motilin; ghrelin; gastric motility DURING A FASTED STATE, THE stomach and small intestine undergo a temporally coordinated cyclic motor pattern known as migrating motor complex (MMC) in dogs (38) and humans (44). It has been established that these coordinated contractions consist of three phases, phase I (period of motor quiescence), phase II (period of preceding irregular contractions), and phase III (period of clustered potent contractions), and the MMC is stimulated by endogenous motilin that is released in the fasted state.Motilin was originally purified from porcine intestinal mucosa in the 1970s, and its molecular structure was determined to be a 22-amino-acid polypeptide. It has been demonstrated that plasma motilin is released at ϳ100-min intervals at the interdigestive state (20,21). Physiological study of motilin in vivo has been mainly performed by using dogs and humans, and endogenous motilin and exogenous motilin have been shown to induce phase III contractions through the cholinergic pathway because atropine pretreatment completely abolished the motilin-induced contra...

The proximal gastric corpus is the most responsive site of motilin-induced contractions in the stomach of the Asian house shrew

“…From in vivo and in vitro experiments using S. murinus, we demonstrated that motilin-induced gastric contractions are mediated through the myenteric plexus (Mondal et al 2011;Sakahara et al 2010). Similar results have been reported in other species (De Smet et al 2009;Kitazawa et al 1995;Mizumoto et al 1993;Ohshiro et al 2008;Van Assche et al 1997).…”

“…Previously, we determined cDNA sequences of S. murinus motilin and ghrelin using PCR cloning (Ishida et al 2009;Tsutsui et al 2009). We then studied the contractile properties of the S. murinus stomach, in both conscious free-moving S. murinus and in an organ bath experiment, and found that S. murinus has almost the same GI motility and motilin response as that found in humans and dogs (Sakahara et al 2010;Tsutsui et al 2009), indicating that S. murinus can be used for GI motility studies. Moreover, many studies have been performed to identify the rodent motilin gene, no convincing results of sequencing have been reported so far.…”

The Gut Peptide Hormone Family, Motilin and Ghrelin

“…During the fasted state, the suncus stomach and duodenum showed clear migrating phase III contractions (intervals of 80-150 min) as found in humans and dogs, and motilin injection also increased the gastric motility index in a dose-dependent manner (Sakahara, et al 2010). Moreover, pretreatment with atropine completely abolished the motilin-induced gastric phase III contractions (Sakahara et al 2010). Since suncus has almost the same GI motility and motilin response as those found in humans and dogs, suncus would be a suitable model to analyze the interaction of motilin and ghrelin in gastric motility.…”

“…Administration of suncus motilin showed almost the same contractile effect as that of human motilin in vitro ). During the fasted state, the suncus stomach and duodenum showed clear migrating phase III contractions (intervals of 80-150 min) as found in humans and dogs, and motilin injection also increased the gastric motility index in a dose-dependent manner (Sakahara, et al 2010). Moreover, pretreatment with atropine completely abolished the motilin-induced gastric phase III contractions (Sakahara et al 2010).…”

Motilin stimulates pepsinogen secretion in Suncus murinus

“…Previous studies demonstrated that gastric contractions are strongly associated with plasma motilin levels and that gastric phase III-like contractions were induced by the intravenous administration of motilin in humans [7], dogs [8,9], and suncus [10,11].…”